Electrical device



Oct. 6, 193 1 L. A. M. PHELAN s r AL 1,826,572

v ELECTRICAL DEVICE Filed March s, 1928 Patented Oct. 6, 1931 UNITED STATES, PATENT orncr.

LOUIS- A. M. PHELAN Am) "rAUL s. BEAR, or ELKHAM', INDIAN ASSIGNOBS, ,IBY" MESNE ASSIGNMENTS, T MINNEAPOLIS-HONEYWELL REGULATOR comrANY, or MINNEAPOLIS, MINNESOTA, A conromnon or DELAWARE ELEcTRicAL DEVICE Application filed March 8, 1928. Serial No. 258,859.

.The present invention relates to an improved form of electrical device applicable to the frequent closing and opening of electrical circuits with-a minimum of deteriora tion in the devlce.

' Our invention comprises an hermetically sealed vessel containing a quantity of metallic conducting fluid, electrodes extending through'a pinch-seal'at one end of the container and adapted to make electrical con- On slightly tiltingthe device, however, one

. portion of the metallic conducting fluid will flow over the dividing dam, and merge with the other portion, thus providin a continuous metallic conducting path fort e electrical current from one electrode to the other.

In order to facilitate the rising, of the conducting fluid over the dam, the inner face of the same is inclined with respectto the central axis of the tube. The sides'of the dam are made preferably straight and vertical so that when the device is tipped in the opposite direction, the metallic fluid will separate practically instantaneously into two portions. By reason of the construction of the dam, this action willoccur on the inclined face thereof, and hence any arcing that may take place on from its upper portion. Both of the eleetrodes may enter the vessel from the-same end; one of the electrodes passing the split portion of the annular dam when the same is so constructed as to permit of this contingency. This makes it possible to employ a pinch seal construction thus lowering the cost of production and simplifying the construc- 6 tion the parting of the fluid, when an. electrical r improved electrical contact device.

' The dam is held in place by a refractor cement. ne of the objects'of our invention is to provide an electrical contact device in which a refractory dam serves to separate a metallic conducting fluid, such as mercury, into two portions, and so to construct the dam that two electrodes, each of which contacts with I a portion of the metallic fluid, may enter the container housing the fluid, dam and electrodes, from the same end.

Another object of our invention is to prO- vide an electrical contact device which comprises a glass container into which two electrodes extend through a pinch seal, one of these electrodes being in contact with one portion of a body of mercury and the other electrode extending through the split in the refractory dam and ending within the annular dam so as to make contact with the second portion of the mercury.

Another object of our invention is to provide an improved electrical contactor construction in which the arcing caused by the separation of the mercury occurs away from the walls of the contactor so that the same may not be cracked or otherwise injured by the heat of the are, while at the same time the conducting wires leading to the electrodes may both enter the container of the contactor at the same end.-

Another object of our invention is to provide an electrode of such characteristics that it will not cause the glass of the container to crack at the seal, and also will have the property of being slightly wetted by mercury.

Other objects will appear in connection with the description hereinbelow, and the drawings that form a part of the present specification. 7 Inthese drawings: A

Figure 1 is a side elevational view of one modification of an electrical contactor made in accordance with our present invention;

Fig. 2 is a top view of the same;

Fig.v 3 is a cross-sectional view showing the appearance of the same, taken along the line 3-3 of Fig. l and looking in the direction of the arrows;

Fig. 4 is a perspective View of theslotted refractory dam;

sumed b meniscuses of liquids in contact Fig. 5 1s a side elevational view of another modification of an electrical contactor em- 7 bodying our present invention;

Fig. 6- 's a. view similar to that of Fig. 1, showing the device in the position when ourrerit is passing through the conductin fluid;

. 1 furth er modification of an electrical contactor embodyin the present invention; and

Figs. 8, 9 am? 10 show the positions aswith various materials.

Referring'to the drawings, it will be seen that our improved contact device comprises a container 11, which may be of glass, or such special glass as pyrex, or of fused silica such as vitreosiland the like. a This container is preferably in the form'of a short tube. One end of the tube 11 is closed by a pinch-seal 12 through which, tightly sealed into the glass,

two conducting wires 17 and 18 extend. These wires may be of platinum, but we prefer to employ a special form of wire known as Dumetwire,'which is copper clad and produces an air-tight seal when imbedded in glass.

Welded to theDumet wires 17 and 18, respectively, there are two metallic contacting electrodes 19 and 20. These niay consist of iron, tungsten, nickel, nickel-iron alloys, chromium-iron alloys, or other similar materials not adversely affected by nor affecting mercury. For reasons that will be more fully set forth hereinbelow, we prefer to emloysubstantially pure nickel. The wold etween the Dumet and the nickel wire lies preferably just within the. inner end of the pinch-sea 12, as the Dumet wire must not be-allowed to come into contact with the 'mercury 13 and 14 as it would contaminate the same. Th'e mercury, as shown in the figures,

forms two portions, 13 and 14, which are separated b a refractory dam 15, the portion 13 prefera ly' being of'a larger mass than the portion 4. a

This dam 15 is preferably made of 'un-' polished'porcelain in order that; a slightly roughened surface is obtained thereover' and inay bein the general form of a split or slotted ring,. as illustrated in Fig.. 4. Although ordinarily made of porcelain,'the

. dam'may. be made of any heat-resistant or I fvided only that th' same is of a nature, that will not react with refractory material such as ignited soapstone, sometimes termed lava or.of a similar hardinert and refractory material, pro- I e mercury, nor cause the contamination of the latter or'the deterioration of-the electrodes. Preferably, also, the

material constituting the dam should be non .-wettable by mercury, and should be slightly roughened so .that'the mercury will ass rapidly thereover' withetttjinany way ad eris aside elevational view 0 a still ing to it. The inner surfaces of this ring are tapered,'so that the ring will be thinner at one end than at the other.

container 11 that it lies athwart the mercury, thereby dividing it into two portions 13., and l twhen the circuit through the'contactor is interrupted.

The outside diameter of the annular dam 15 is slightlyless than the inside diameter of the glass container. The, dam is attached to the glass walls, and held rigidly in position, by a refractory and electrically insulating This annular dam 15 is so disposed within the tubular glass cement, which may consist of a pasty mixture of asbestos, aluminum oxide and sodium silicate. This cement forms .a mercury-tight joint 22 between the glass walls of the container and'the outer periphery of the refractory dam 15 and thus eliminates allpossibility of a short circuit. being established underneath. the dam. It is desirable that such cementhave a ooefiicient of expansion approximately the same as that of the material composing t e container, as otherwise the alternate heating andcooling of the dam may cause the container or the dam to crack by reason of the strain produced by unequal expansion ofthe container and the dam. A suitable formula or compound for a cement, when the container is made'of glass and the same is made of a good grade of porcelain, is:

makea syrup-like'paste.

The nearer the coeflicient of expansion of .the glass is to that of the porcelain dam the less asbestos is to be used in the above formula.

Magnesium silicate, MgSiO magnesium oxide, MgO, may replace the asbestos. Thesodium silicate may also be diluted with some water before use. Another cement that has proven satisfactory is made. up of lead phosphate, Ph (PO and sodium silicate. This is especially desirable when the glass employed has a high' coefficient of expansion.

In'fpositionin the dam 15, the split portion or slot is placed uppermost, and .the..dam is spaced nearerthe ,end'through which the electrodes enter the'container. The'cement -is applied; to the outer surface of, the annular dam in sufiicient amounts to completely fill the space remainin' between the dam and the interior surface 0 the glass, whereupon distance into the container and terminates on a downwardly bent portion abouthalf-way between the glass pinch-seal and the straight 1,4 t and 6.

An amount of mercury, or similar electrical vertical sideof the dam 15, as shown in Figs.

conducting fluid, suflicient to bridge the dam when the entire device is slightly tilted, as shown in Fig. 6,'is placed in the container. There should, however, be insufficient mercury to bridge the. dam when the container is in a substantially horizontal position, or

slightly inclined in a direction opposite to that shown in Fig. 6.

Theinsertion of the Dumet wire with the electrodes welded thereto can be accom-.

plished by machinery, and the method for so doing is more particularly described in a copending application, Serial No. 228,043, filed October 22, 1927 V However, in order to prevent the possibility of the electrode from cracking the glass f in the seal, we prefer to employ substantially pure nickel for making the electrodes. We have found that a slight spa'ce remains between the nickel and the glass, forming a sort of air pocket or gas pocket. This we account for on the theory that the'nickel, be-

' ing' heated substantially to red heat during I of the atmosphere, and these escape from the surface of the nickel'electrode during the the operation of sealing'the-Dumet wire and electrodes into the glass, becomes oxidized with the formation of a film of nickel oxide.

As the tube. after complete assembly is exhausted of all air through a tubulature forni- .-ing apart of the glass container (of which t'ubulature only the remaining tip 21 is shown in the drawings), and filled with hydrogen and heated to remove all traces of oxygen, and again exhausted and refilled with hydrogen, it is highly probable that the film of nickel oxide is reduced to metal, thus slightly diminishing the diameter of the electrodes and thus leaving the minute space between it'and the glass. Another possible explanation is that nickel always has absorbed or dissolved in it a small amount of the gases sealing operation, thus pushing the glass away from the nickel.

Irrespective of thecorrect theoreticalexplanation of the phenomenon just described,

' the fact remains that even though the nickel I electrodes may become heated by the passage of electric current through them, the resultant expansion is compensated for by the minute space between them and the glass seal, and the crackin of the'glass at the point is prevented. With materials other thannickel, difficulty caused by end expansion has been encountered. We have, hbwever, by our use of nickel electrodes, overcome this difficulty,

= andconsider this feature as one of the objects attained by our invention.

Another decided advantage inherent in the use of nickel electrodes is the fact that the nickel will not contaminate the mercury. Furthermore, a better electrical contact is formed between nickel and mercury by reason of the slight coating or wetting of the nickel by the mercury. This causes a change in the nature of the meniscus at the point where the nickel electrode dips into the merbelow its surface, as seen in Fig. 9, A nickel rod, however,is partially wetted by mercury and practically merely punctures the surface with a hardly appreciable meniscus, as shown in F ig. 10.

The resultantelectrical contact is more perfect and has less resistance than one between mercury and some metal which is not at all wetted by the same. Instead of making the upper electrode 19 with a'rectangular bend, as shown in Fig. 1, we may adopt the construction of'the modification illustrated in Fig. 5. In that case the electrode 19a bends downwardly almost immediately after entering the container 11 and terminates at relatively the same point within the annular I dam 15 as does the rectangularly bent elec-- trodelt) in Fig. 1. This makes it possible to use a short electrode, and the internal resistance of an electrical contactor made accordbe lower than that of one made according to the modification shown in,Figs. 1, 2 and 6. Both constructions, however, are to be con sidered within the scope of our present invention. Again, it may be desirable tomodify either one of the previous structures in order that the electrodes19 or 19a terminate outside of the annular dam as shown mor particularly in Fig. 7.

One of the particular advantages of our ing to the modification shown in Fig. 5 will improved construction liesin the ability to I employ a mechanically made pinch-seal through which both of the conductors welded to the electrodes enter the container 11. The

upper split or slot16, in the substantially an- "nular dam 15, permits one electrode to contact with the portion 13 of the mercury lying in that section of the container furthest away from the pinch seal.

It is to be understood that the containerll besideshousing the mercury and electrodes contains an atmosphere of a gas inert to mer-" cury and nickel as, for example, hydrogen. This gas may be either at substantially atmosla o pheric, pressure, or above or below that pressure. The use of a pinch seal such as that shown also makes it possible to employ a shorter tube and less mercury.

Of course, it is apparent that .the' split sleeveor dam 22, as shown in Figs. 3 and 4, is not essential to the employment ofa pinch seal construction because the construction shown in Fig. 5 may be employed which does not necessitate the use of a dam having a split portion. I

Obvious modifications in the construction embodying our improved form of-electrical contactor are to be construed as within the scope of our invention, folwhich we claim:

1. A tiltable electrical contactor comprising an hermetically sealed elongated container, electrodesof a material not adversely atlected' by mercury entering said container at the same end thereof and spaced from one another within said container and longitudinally thereof a split annular dam da of arefractorymaterial nonwetta-ble by mercury disposed within the container Wholly beyond where said electrodes'enter the same,

and a body of metallic conducting fluid adapted to establish electrical connection between a body of metallic conducting fluid adapted to establish electrical connection between the electrodes, said body of fluid being in sufcient amount to cover said dam when the contactor 1S. tilted to the conducting position but 1n insuflicient amount to cover said dam when the contactor is tilted into interrupted position, one of said electrodes lying for a portion of its length Within the split portion of the said dam. p r I 3. A tiltable electrical contactor-comprisingan hermetically-sealed container, electrodes of a material not adversely aife'cted by :nercury, a split dam of a refractory mate-- rial ofsubstantially-tubular form and nonwettable by mercury located wholly beyond 'where said electrodes-enter the container and a body of metallic conducting'fiuid adapted Jo establishielectrical connection between the electrodes, said body of fluid being in sufficient amount to cover said dam when the contactor is tilted to theconducting positionbut in insuflicient amount to cover said dam when the contactor is tilted into interrupted positainer the electrodes,

enter the tube, passing at least partially within the split tion, one of said electrodes" lying atleast partially within the split portion of the dam and terminating within said dam.

4. Atiltable electrical contactor comprising an hermetically sealed container, electrodes of a material not adversely affected by mercury entering said container at the same end thereof, a split annular dam of a refractory material nonwettable by mercury of substantially tubular form, said tube having tapering sides and being located wholly beyond where said electrodes enter said conand a body of metallic conducting fluid adapted to establish electrical connection between the electrodes, said body .of fluid being "in suflicient amount to cover said dam when the contactor is tilted to the conducting position but in lIlSlllfiClBIlt amount to cover said dam whenthe contactor is tilted into intermediate position, one of, said electrodes terminating withm said 5. A tiltable'electrical contactor comprising an hermetically sealed tube, metallic electrodes passing through a pinch-seal at one end ofsaid tube and sealed therein, a split annular dam of refractory material positioned on the interior of said' tube and disposedwholly-beyond where said electrodes at least one of said electrodes portion ofsaid dam and a body of mobile electrically conducting fluid adaptedto establish electrical connection between said electrodes, and an atmosphere of inert gas in said tube.

6. In an electrical contactor of the type described, the combination of a substantially annular split refractory damsecured'to the interior of the container and withan elongated electrode passing at least partly through the split portion of said dam. I

7 A' t'ltable electrical contactor comprising an hermetically sealed container, electrodes contained therein, a mobile, body of electrically conducting fluid in contact with one of said-electrodes but adapted to be divided into two bodies of mobile conducting fluid, one of which remains in contact with one electrode, a split annular dam disposed wholly beyond one of said electrodes and dividing said bodies of mobile conducting fluid into two portions and an atmosphere of inert gas within said container, at least one of said electrodes passing at least partly through the splitjportion of said dam.

- 8; In an electrical'contactor of the type contact with a body of mercury, a split annular refractory heat-insulating dam adapted to holdsaid body of mercury in contact with said electrode, a second electrode in said contactor and passing for a portion of its length through the split in said dam,

described, the combination of a metallic electrode in said contactor in permanent a second body ofmercury adapted to contact trode inwardly disposed in said contactor and in permanent contact with a body of mercury, a split annular heat-insulating dam of re- .fractory material adapted to hold said body of mercury in contact with said electrode, a second electrode passing out of the container from the same end as the first electrode and passing for a portion of its length through the dam; a second body of mercury adapted to contact with said second electrode, the quantity of said second amount of mercury being such that on tilting the contactor said second body of mercury passes over said dam and, merging with the first body of mercury, establishes electrical connection between the first and second electrodes.

10. In an electrical contactor of the type described, the combination of-a nickel electrode inwardly disposed in said contactor and in permanent contact with a body of mercury, a heat-insulating split annular dam of I refractory material adapted to hold said body of mercury in'contact with said electrode, a second electrode" entering said contactor at the same end as the first electrodeand passing for a portion of its length through the slot in said. dam, a second body of mercury adapted to contact with said second electrode, the quantity of said second amountof mercury being such that on tilting the contactor said secondbody of mercury passes over said dam and, merging with the first body of mercury, establishes electrical connection between the first and second electrodes. f

11-.- A tiltable electrical contactor comprising an hermetically sealed container, two

electrodes entering said container through a, pinch seal at one end thereof, a damconsisting of a split tube of refractory material not adversely affected by mercury in said container and disposed beyond one of'said electrodes. the second electrode passing through the slot in said dam, a body of mercury adapted to establish a path for electric urrent between said electrodes and of sufficient quantity to cover said dam when the contactor is tipped into conducting position,

- and an atmosphere of hydrogen within said v 60; L

container. 7 p

12. A tilt-able electricalcontactor'comprisng an heremtical ly sealed glass container, Dumet leading-in wires sealed in the wall thereof, nickel electrodes within said container that are attached to said Dumet wires .an hermetically sealed vessel containing a metallic conducting fluid and two electrodes entering said vessel through a pinch-seal at one end thereof, means for dividing the conducting fluid into two unequal portions comprising a tubular dam of refractory material, said dam being split to permit one electrode to traverse said dam, and contact with She conducting fluid at the far side of said 14. An electrical contactor comprising a hermetically sealed elongated container, a plurality of electrodes sealed in one end thereof through the medium of a pinch seal and spaced from one another in said seal transversely of the container and in said container longitudinally thereof, a refractory dam disposed interiorly of said container, one only of said electrodes terminating within the area of said dam'and the other of said electrodes terminating at the adjacent end of said container and spaced from the container wall and from the adjacent end of said dam,

and a body of mercury housed in said 0011- tainer for making and breaking the electric circuit between said electrodes.

15. An electrical contactor comprising a hermetically sealed elongated container, a plurality of electrodes sealed in one end thereof throughthe medium of a pinch seal, a refractory dam disposed interiorly of said con- 1 tainer, one only of said electrodes terminating within the area of said dam and the other of said electrodes terminating at the adjacent end of said container and spaced from the container wall and from the adjacent end of u. said dam, and a body of mercury housed in said container for making and breaking the electric circuit between said electrodes, said electrodes being spaced from one another transversely of said. container at the pinch II seal and longitudinally of said container at I their exposed contacting surfaces.

from the pinchseal to provide a recess to receive a body of mercury, said dam having an inclined surface that slopes downwardly away from said pinch sea-l, one of said electrodes terminating within said recess intermediate said dam and said pinch seal and the other electrode terminating within the area. of said dam, and a body of mercury filling said recess and the excess of said mercury being movable on the tilting of the contactor for making and breaking the electric circuit between said electrodes;

17. An electrical contactor comprising a hermetically sealed container, a plurality of electrodes sealed in one end thereof, a refractory dam disposed interiorly of said container and spaced from thes'ealed end of said 1 container to provide a recess to receive a body of mercury, said electrodes -being spaced Q transversely of said container at the seal and longitudinally of said container at their exposed contacting surfaces and one of said electrodes terminating within said recess in- Y termediate said dam andsaid seal and-the other electrode terminating within the area ofjsaid dam, and a body of mercury filling said-recess and the excess of said mercury being movable on the tilting of said contactor for making and breakingthe electric circuitbetween said electrodes. I 18. An electrical contactor comprising hermetically sealed container, a plurality of electrodes sealed in one end thereof through the medium of. a pinch seal, a refractory dam disposed interiorly of said container and spaced from the sealed end of said-container to provide a recess to receive a body of mercury, said electrodes being spaced transversely'of said container at the pinch seal and 40 the lower electrode terminating within said recess intermediate said dam and said pinch seal and the upper electrode extending longitudinall ,of said container and terminating within t e'area of said dam, said dam having an inclined surface sloping downwardly in the direction of the electrode that terminates within the area of the dam, and a body of mercury filling said recess and the excess of. said mercury being movable on the tilting of said contactor for makin and breaking the electric circuit between said electrodes.

In witness whereof we have hereunto subscribed our names.

- LOUIS A. M. PHELAN. 4 PAUL S. BEAR. 

